The present invention relates in general to the provision of an inner tube safety system for a partially puncture-proof, vehicular, pneumatic tire of the "runflat" variety. More particularly, the present invention relates to a pneumatic tire comprising means for partitioning the interior thereof into two inflatable annular chambers, one of which surrounds the other so if punctured will deflate to the exclusion of deflation of the inner chamber it surrounds.
It is already known to provide an inner tube safety system for pneumatic tires that comprises:
(A) A SO-CALLED PRIMARY, RADIALLY INTERNAL, CONTINUOUS, ENDLESS ANNULAR INNER TUBE MADE OF A SUBSTANTIALLY INEXTENSIBLE FLEXIBLE MATERIAL IN ORDER TO MAINTAIN A SUBSTANTIALLY CONSTANT CROSSSECTIONAL PERIMETER, THE TUBE BEING ADAPTED TO SURROUND CONTIGUOUSLY AND FIT INTO THE WELL OF A VEHICULAR WHEEL RIM, THE TUBE HAVING AN OUTSIDE DIAMETER THAT, IN ITS MOUNTED INFLATED STATE, IS SUBSTANTIALLY LESS THAN THE INSIDE DIAMETER OF THE CROWN REGION OF AN INFLATED TIRE THE TUBE IS TO BE ASSOCIATED WITH, THE TUBE HAVING A CONVENTIONAL INFLATION VALVE DESIGNED TO PASS THROUGH SAID RIM; AND
(B) AT LEAST ONE SYSTEM OF A SO-CALLED SECONDARY RADIALLY EXTERNAL INNER TUBE MEANS MADE OF ELASTICALLY EXPANSIBLE OR DILATABLE MATERIAL, CIRCUMFERENTIALLY SURROUNDING COMPLETELY, CONTIGUOUSLY, AND SUBSTANTIALLY CONCENTRICALLY THE PRIMARY INNER TUBE, AND FILLING OUT, IN THE MOUNTED STATE, THE BALANCE OR THE REMAINING VOLUME OF THE AVAILABLE INNER SPACE OF THE TIRE, THE SECONDARY INNER TUBE MEANS BEING CONNECTED, PREFERABLY DETACHABLY AND HERMETICALLY WITH THE PRIMARY INNER TUBE BY AT LEAST ONE "SPECIAL VALVE" CAPABLE OF (1) OPENING AUTOMATICALLY TO COMMUNICATE THE INTERIORS OF THE PRIMARY AND SECONDARY TUBE SYSTEMS WITH ONE ANOTHER WHEN THEY ARE UNDER A MUTUAL PRESSURE EQUILIBRIUM AND (2) CLOSING AUTOMATICALLY WHEN THE SECONDARY OR OUTER TUBE MEANS IS PUNCTURED AND LOSES ITS PRESSURE EQUILIBRIUM WITH THE PRIMARY OR INNER TUBE. Such a "special valve" (or valves) is disclosed in copending U.S. patent application Ser. No. 703,339, filed July 8, 1976 now U.S. Pat. No. 4,054,169, dated Oct. 18, 1977, and assigned to Uniroyal, a Societe Anonyme, which assignee is the same assignee of the instant application, the contents of which is fully incorporated by reference herein.
The above known system is attended by the drawback of requiring a structure of relatively complex and costly primary inner tube constituent material due to its necessary inextensibility property.